A plasma etching technique for a target object is important in manufacturing devices. In the plasma etching technique, a plasma density distribution in a processing space needs to be controlled to adjust an etching rate distribution of a target object. As a technique of controlling a plasma density distribution, there has been known a technique of controlling a plasma density distribution by generating a magnetic field in a processing space where an electric field is formed. Such a technique is described in, for example, Patent Document 1.
A plasma processing apparatus described in Patent Document 1 is a parallel-plate type plasma processing apparatus including an upper electrode and a lower electrode. This plasma processing apparatus generates a magnetic field which is symmetric in a radial direction with respect to a central axis line of a target object, i.e. a wafer, in a processing space. To be specific, in the plasma processing apparatus described in Patent Document 1, a mounting table serving as the lower electrode is provided in the processing space and the wafer is mounted on the mounting table. A ceiling portion of a processing chamber, which partitions the processing space, serves as the upper electrode, and multiple permanent magnets are provided on an upper surface of the ceiling portion. The multiple permanent magnets are arranged along multiple concentric circles around the central axis line of the wafer and also arranged in the radial direction with respect to the central axis line. In the plasma processing apparatus, a vertical electric field is generated in the processing chamber, and by setting directions of magnetic poles of the multiple permanent magnets at the processing space side, a magnetic field distributed in a radial shape is generated in the processing space. Thus, electrons in plasma are subject to Lorentz force, and perform a drift motion to be revolved around the central axis line of the wafer. A speed of the drift motion is inversely proportion to intensity of horizontal magnetic field components in a radial direction with respect to the central axis line of the wafer. Therefore, in an area where the drift motion is performed at a low speed, a staying time of the electrons becomes long. In an area where a staying time of the electrons is long, dissociation of a processing gas becomes accelerated. As a result, a plasma density distribution in the processing space can be adjusted.
Patent Document 1: Japanese Patent Publication No. 4107518
Meanwhile, when etching a multilayer film formed of multiple films different from each other in a kind of a film and a thickness of a film, a high frequency power for plasma generation to be applied to an upper electrode or a lower electrode and/or a high frequency bias power for ion attraction to be applied to the lower electrode may be changed depending on a kind of a film and a thickness of a film. If the high frequency power and/or the high frequency bias power are changed, the plasma density distribution in the processing space is also changed.
However, in the plasma processing apparatus described in Patent Document 1, since the positions of the multiple permanent magnets are fixed, an intensity distribution of the horizontal magnetic field components cannot be adjusted. Therefore, in the multilayer film formed of multiple films different from each other in a kind of a film and a thickness of a film, when each of the multiple films is etched, a plasma density distribution cannot be adjusted. As a result, an etching rate of each film may be non-uniform in a radial direction from the center.
Under these circumstances, in this technical field, it has been demanded to suppress non-uniformity of an etching rate depending on a position when etching each film of a multilayer film.